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Old 16-03-2012, 09:48   #1
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Low Oil Pressure at Low Revs

Hi all. The oil pressure on my Volvo Penta TMD 31B drops as I back off the revs. The pressure drops to about 50% of that at 2000 rpm when I back the throttle to idle. Is this indicative of a problem, or normal oil pressure response to slowing the engine down?
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Old 16-03-2012, 10:04   #2
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Re: Low oil pressure at low revs

It is normal for the oil pressure to drop as the revs are backed off. 50% seems a bit high. What is the high and what is the low? If it goes from 60lbs down to 40 you are ok. If it goes from 40 down to 20 you might be looking at a real problem. Several things can cause this big change. The first thing is to make sure the oil and filter are fresh. Plugged filter and thick used oil can cause this problem. You will also notice a bigger change when the engine is cold. Beyond the routine maintenance one has to look at things like oil bypass valve springs, worn oil pumps, worn main bearings and the list goes on.
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Old 16-03-2012, 10:09   #3
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Re: Low oil pressure at low revs

It is normal for oil pressure to drop with RPM,,also with engine reaching operating temperature.
Oil Pressure is a measurement of resistance of the oil flow,,NOT the Flow itself.
You can be getting great flow and low pressure and it wont mean a thing.
On the other hand,,if your oil pressure is low all the time, then its an indication of worn Bearings etc,,and time for a rebuild.


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Hi all. The oil pressure on my Volvo Penta TMD 31B drops as I back off the revs. The pressure drops to about 50% of that at 2000 rpm when I back the throttle to idle. Is this indicative of a problem, or normal oil pressure response to slowing the engine down?
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Old 16-03-2012, 10:35   #4
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Re: Low Oil Pressure at Low Revs

Oil Pressure is directly connected to main bearings and their wear. Pressure will drop over time with wear. A drop in pressure is normal for most engines when they come off sustained revs. An abnormally high, low of or lack of pressure needs your attention. Change your oil and filter religiously. Crank your engine with ignition off prior to start if possible to get oil moving thru engine. Learn what is normal for your engine. Your engine manual should give you high and low limits as long as your with in those no worrys.
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Old 16-03-2012, 10:40   #5
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Re: Low oil pressure at low revs

How old is the engine? Hi time or low time? Is the oil diluted from fuel getting into the sump? Does your gauge show in PSI or just a green and red zone? The first thing I would do is change the oil and see if that makes any difference . Make sure you are using the correct weight and grade of oil, and see if the oil you drain out of the engine seems to be thinner than what you are putting back in, or if the used oil smells like diesel. Use an actual Volvo oil filter even though they cost way more. If your oil gauge doesnt show in actual numbers, install one that does and see if the low pressure is within the manufacturers tolerances . You may find that you dont have a real problem. Since you didnt say anything about engine temperature, I assume that is not the problem, but if you only have a over temp warning light you might be running on the edge of overheating ,which could cause the low oil pressure. Give us some more info and you will get more and better advice. Hope this helps.____Grant.
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Old 16-03-2012, 10:56   #6
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Re: Low Oil Pressure at Low Revs

At low rpm, my Perkins dropped a lot... from about 60 to probably 20. It was a nearly new engine...
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Old 16-03-2012, 11:07   #7
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Re: Low Oil Pressure at Low Revs

normal, is the alarm coming on when you slow down?
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